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Olympus PEN & OMD Flash mod to reduce recycling time & battery

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I Haven't received the capacitor yet, but I'm thinking about implementing a cell phone led flash... this will be the easiest (I think :)).

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What are your thoughts on how to implement LED trigger/quench since the voltages floating around are not exactly suitable to say the least!



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It would be great If you could reverse engineer the pin layout and protocoll for controlling the flash!

This would open up some options for sure. My thinking is that it would be possible to do a simple

LED TTL strobe as it seems to me that all logics are in the camera, so that the camera control the strobe

with a trigg and quench signal. (I'm guessing based on images earlier in the thread.)

It would be good if you got the oportunity to take some more pics on the hotshoe connections and the circuits

top and bottom.

For making a LED strobe, i would choose to use a separate lithium battery, but I suppose it should be possible

to use the camera battery to, as there must be a pin with the 4.2 V from the camera battery for charging the

the standard flash.

However, I have made good with non-TTL for now, so maybe I should try to se if I like it before building something elaborate


BTW, interesting mod on the RX100mk2, As it does have a hotshoe it seems better to use a microstrobe rather than to cripple

it. However, it's an excelent mof for the mk1 without hotshoe!

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I opened up the rest of the flash at the weekend and I suspect that the complex little circuit precludes reverse engineering. It is a double sided pcb with a bunch of surface mount stuff. I could not find one of the two 10-pin SMD packages when I searched online. Personally I think modding a circuit that already does the job as Olympus intended is the best route.


I am going down the other track and have ordered a spare xenon for a mobile phone camera (Nokia 6022) to see if it is lower power.



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I've opened it up also... I'm trying to see the writing on the chip with no success... Clownfish do you a pic of the circuit? I'm attaching mine... but I can't seem to see what is written on the main chip (looks like a small microcontroller).




If we look at the connector from left to right top row first then.


1 - NC (Not Connected)

2 - NC


4 - NC

5 - NC

6 - NC

7 - NC

8 - NC

9 - NC

10 - NC

11 - NC

12 - NC

13 - NC

14 - ??

15 - ??


17 - ?? (Connected also to 30)





19 - NC

20 - NC


22 - NC

23 - NC


25 - NC

26 - NC


28 - NC

29 - NC

30 - ??

31 - NC

32 - ??

33 - ??


So there are 5 pins working... 14,15,17 (30), 32, 33 So who will lift the glove to do the reverse eng...

Edited by AYahoo

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So a smaller tube arrived and I put it in. I think it was faster. However testing of recharge time was curtailed by a bigger issue. With my 50mmf2 attached as soon as I go smaller than F16 on my EM-1 the FL-LM2 gets unreliable and more often than not completely over exposes. Perhaps I have damaged my FL-LM2 so I need to buy another before I can reach any conclusions...


EDIT: I put the original tube back in and the problem is without any UW strobe or housing. Plus I did a full reset in case I had mucked up a setting. The flash/camera might have had this problem from day one so glad I've been fiddling and spotted this since it would have made shooting underwater very haphazard.

Edited by simonknee

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OK I was able to do some testing even with the >F16 fault.


These are the original tube (large) and a tube from a Nokia phone.




EM-1 in Nauticam NA-EM1 housing optically firing a Sea&Sea YS-01

Setting the camera to F14 and shooting the same test scene

YS-01 lights green to show TTL.

Pictures expose the same with either bulb.


But the nokia tube is draining the battery MORE!

It takes three blinks of the flash icon on the LCD for the original tube.

Yet four blinks for the smaller Nokia.

In both cases the YS-01 recharges in under a second but it is taking 3-4 seconds for the FL-LM2.


Ho hum - to be fair I have no specs on the nokia tube other than it's size.

Worth a punt mind.



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Good to se your experimenting on!

Just very quick comment:

A flash tube does not work like a light bulb with different power ouputs.

The flash tube is a gap when not ignited, once the tube ignites and the plasma is created, it acts basically like a short circuit.

If you get a smaller tube, it has different characteristics, like what voltage you need to ignite it, and what power it can handle without beeing damaged.

But once you ignite it it is basically a short circuit just like the bigger tube, but probably slighly lower resitance still. It will empty you capacitor completely if not quenched by a cicuit.



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Anyone could tell me how to open FLM-2 flash (the new one that comes with the OMD EM5 or EM1)?


For FLM-1 it's easy because you see two screws, but for the FLM-2 I don't see it...


I have changed the original capacitor of the FLM1 unit with 1uF capacitor and it works well in manual mode using OMD EM5 and S&SD1.



The problem is that this unit is higher than FLM2 (several mm) and when I put the camera+FLM1 inside the Nauticam Housing, the head of the flash is not pointing directly to the FO holes...


Now I have a second hand FLM2 and I would like the same capacitor change....

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Screws are all underneath sticky tape. Flip the flash up and remove the bit of tape. You will find the ones you need to take the top cover off.


Sent from my Nexus 4 using Tapatalk

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Ok, Great!!

Thanks a lot, simonknee!!

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Testing of resistance mod:


(my erratic exposure above F16 was down to the erratic closing of the aperture blades on my 50f2, I am now testing with my 11-22 @22mm as it is a happy snapper at all apertures)


So in an effort to increase the resistance of the tube (and use less power) I added some resistance.


I soldered in a 1ohm 5watt wirewound directly to the anode of the tube (pic later).

The flash still worked but this made little difference to recharge times.

There is plenty of power going through here which soon destroyed a 10ohm 1W carbon resistor (nice internal explosions).

So digging about in the component drawers I settled on a 6R8 (that's 6.8ohms) 22W wire wound resistor.

I will try and do the maths on what is a suitable wattage later - suffice to say please be careful if you try this, no fires please.


When testing in the housing with a pair of Sea&Sea this shaved 1/3 off the recharge time compared to an original FL-LM2.

However reviewing the images from my resistive flash showed that as the aperture got smaller the exposure got brighter (tried another lens to confirm)

AT F10 exposure was the matched, at F22 it was approximately 1 stop brighter using the resistive flash.

I guess the mod upsets the pre-flash a bit and causes the EM-1 to think it needs more light.

So I stopped down the flash (on the EM-1) to match exposure and of course recharge time was even quicker.

The camera was able to keep up with the recharge of the S&S (YS110a & DS-01) on a dining room table test at least.


This is a double-edged sword for me since though it appears predictable it means there is more to remember to adjust which isn't really the ethos of TTL. Though adjusting flash exposure at the camera is much easier than in manual on each of the strobes.


Onwards and sideways




EDIT: As to this mod upsetting the pre-flash I did notice that the light produced by the flash dropped away more dramatically than the original as you moved down the full, 1/2, 1/4, 1/8 ... flash settings (tested on it's own out of housing). The resistor mod does appear to adversely affect shorter flash times (perhaps it causes a tiny start delay?). This does mean that there may be issues with short flash durations even in the housing - only UW testing will tell if these shorter durations are even needed.

Edited by simonknee

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Hi Folks

I know this is an older thread, but how did it all end up?

Is changing the capacitor to 33uf to reduce recycle time a reasonalbe mod?

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